Melanin that is a dark brown pigment functions to block UV rays, and thus functions to protect the skin from UV rays. Thus, when the skin is exposed to UV rays, a large amount of melanin is produced in the body in order to protect the skin. The skin color is determined by the amount of melamine. The more the amount of melanin, the darker the skin color. Thus, the production of a large amount of melanin causes discoloration, spots, freckles, dark spots and so on. Accordingly, substances that inhibit melanin production can have skin whitening effects.
Tyrosinase is an enzyme that converts tyrosine to dopa which is then oxidized to dopa quinine. Dopa quinine is then polymerized to form melanin. In other words, tyrosinase acts as an enzyme that catalyzes melanin production, and thus substances that inhibit tyrosinase can have skin whitening effects.